The firestop collar arranged around pipes or cables comprises intumescent material that expands upon exposure to heat, closing off the penetration as tightly as possible, so as to prevent propagation of the fire. Depending on the diameter of the penetration, the firestop collar can be arranged at an outer end of the penetration, for example, on the wall or floor/ceiling, or else directly in the penetration. When the firestop collar is arranged at the entrance to the penetration (wall mounting), it is normally fastened to the wall or floor/ceiling by means of brackets. Such firestop collars are described, for example, in German applications DE 10 2008 031 018 A1, DE 102 17 174 A1 and DE 198 52 120 A1. If the firestop collar is arranged in the penetration in such a way that only a small part of the firestop collar projects beyond the penetration, no additional bracket is needed as is the case with wall mounting. This is also referred to as firestop bandages or firestop strips. Such firestop collars are described, for instance, in German utility model DE 201 10 973 U1, German patent application DE 103 05 903 A1 or German patent application DE 10 2008 059 564 A1. The firestop collars, which are mounted so as to have an overhang, that is to say, which are wrapped around the pipe so as to extend partially beyond the penetration, are employed with a sufficient overhang, especially when it comes to thin-walled plastic pipes, so that, in case of fire, the intumescent material of the firestop collar can be heated up early enough to the temperatures needed for the expansion. When the firestop collar is completely integrated into the penetration, these temperatures are often only reached at too late a point in time, so that the plastic pipe collapses before the firestop collar starts to expand.
As set forth in the invention, the term “firestop collar” comprises all types of wrappings that are wound around pipes or cables and that have firestop properties, especially firestop fabric collars, that is to say, strips of intumescent material that are wrapped with a fabric strip, firestop bandages and firestop strips which are such that they are made of a material or applied onto a carrier that is so flexible that it can be pushed in a specific direction by the intumescence pressure of an expandable material. This list is provided by way of an example and should not be constructed in any limiting manner.
A firestop collar in the form of a firestop strip having an overhang is shown by way of an example in FIG. 1. A wall 2 has a penetration 3 through which a pipe 1 runs that extends along the longitudinal axis A. A firestop collar 4 which is, for instance, a fabric strip comprising intumescent material 5 surrounds the pipe 1 in the penetration 3 in the circumferential direction with an overhang, so that it comes to rest partially between the pipe 1 and the penetration 3. The remaining opening 7, in other words, the gap left between the firestop collar 4 and the penetration 3, can be filled with mortar or gypsum 6, which optionally can have firestop properties. This affixes the firestop collar 4 in the penetration 3.
These prior-art arrangements, however, entail the problem that some of the intumescent material 5 spreads in the axial direction (that is to say, essentially parallel to the longitudinal axis A of the pipe 1) and is squeezed out at the opening of the penetration 3 on the side of the wall. Moreover, the intumescence in the area of the overhang is not oriented and the intumescent material 5 spreads in all directions. As a result, intumescent material is lost and is then not available to close off the penetration 3. A correspondingly large quantity of intumescent material 5 is normally employed in order to remedy this problem.